1. Field of the Invention
The invention relates to a deposition apparatus and a method of forming a film. More particularly, the invention relates to a chemical vapor deposition apparatus and a method of forming a parylene film.
2. Description of Related Art
Parylene film has superior water resistance and oxygen resistance, high transparency and insulation, and capability in preventing rust, corrosion, and efflorescence. Thus, parylene film is usually adopted as the gas barrier layer on the surface of the flexible plastic substrate in current flexible displays.
In conventional fabrication, a parylene film is generally formed by a chemical vapor deposition (CVD) method. Firstly, powdered parylene is placed in an evaporator and heated to 150° C. for evaporating powdered parylene. Parylene gas is then passed to a pyrolysis chamber and heated to 650° C. for pyrolysis. Next, parylene monomer is delivered to a deposition chamber and deposited on a substrate.
Generally, in a CVD apparatus for performing the aforementioned CVD method, throttle valves are disposed respectively between the evaporator and the pyrolysis chamber and between the pyrolysis chamber and the deposition chamber for adjusting the pressure in the CVD apparatus and for controlling the flow of parylene through the throttle valves for adjusting the thickness of the parylene film deposited on the substrate. However, the evaporated parylene gas easily deposits in an environment under 150° C. Accordingly, the parylene film is usually formed on the throttle valves, and this leads to damages of the throttle valves and requires costly replacement fees. In addition, when powdered raw material is replaced with aqueous raw material to overcome the above problem, the fabrication cost significantly increases as the price of aqueous raw material is about 100 times of that of powdered raw material.
Other than the foregoing CVD apparatus, another CVD apparatus for forming the parylene film is introduced. In this CVD apparatus, throttle valves are not disposed between the evaporator and the pyrolysis chamber and between the pyrolysis chamber and the deposition chamber. In other words, the evaporator, the pyrolysis chamber, and the deposition chamber are connected to one another, and the damages of the throttle valves can therefore be avoided. Nevertheless, in the process of forming the parylene film with this CVD apparatus, when the parylene material has been consumed, the apparatus needs to be stopped to refill the parylene powder and cool the temperature therefore to room temperature, thereby failing to fabricate continuously.